I got these from a guy who says they came from Florida (they don't look like P velifera or P latipinna though). He gave me 5 of them (one has since perished) and they look like some sort of wild type molly. They are NASTY! They came with a pair of Florida Flag Fish (Jordonella floridae) and I thought these were being beat up by the flag fish. Nope! These guys (or ladies rather) killed the male flag fish, and the female is cowering in a corner.
When I put them in, they were shimmying, so I added a little salt and raised the hardness gradually by dropping in a cuttle bone.